Hi all,

I'm building a reasonable clone of the Roland System 700 "Block 1" out of the excellent Pharmasonic modules into a 9u x 84hp rack.

The Pharmasonic Modules themselves are 'immutable', in that I'm not looking to swap out/replace/improve on any of them, as that is kind of the whole point of the project, but I'm actively looking for any thoughts you have on the 'other' modules that are either needed (power supply, line-level output) or very handy (MIDI input, Audio input, DSP effects). Obviously there's not a whole lot of space left in the rack to work with, so compact is good.

Let me know what you would add (or remove) within the space available if this were your project! Any input is appreciated.

Pharmasonic SYS-700

First up, if this is intended to replicate Block 1, I wouldn't have put it in this case. Erica's Monster Case (2x 126hp) is a much better fit here, with the same space, internal power, and the two-row form factor (or something better approximating it) of the original. The 84hp width cabs are better suited here to stand in for the wing cabs, and since (I assume) you have three already, you have the basis for two of your wing cabinets.

Block 1's audio input is already there...it's the "amplifier", which you'll notice has a similar gain setup to the ARP 2600 input amplifier. That extra module can therefore be eliminated.

DSP effects...uhm, no. Part of the key to the System 700 sound (just like in the Buchla 100) is the spring reverb. The electromechanical design introduces a lot of odd behaviors, nonlinearities, etc that you just can't model well with a Spin FV-1 chip (the basis for the PICO DSP). You're also missing a panner here. And the output stage needs metering to match up with the original. For the reverb, I'd be inclined to go with G-Storm's Electro Spring Tank as the drive module, then select a long Accusonics tank (mounted internally) to get the right sort of sound there. The "panner" that Block A has, though, isn't a VCA-based autopanner but a three-channel stereo mixer, everything under manual control. So something simple but stereo like Doepfer's A-138s would be just fine. Then for your output, I'd go with something that has dual balanced 1/4" outs plus metering, like Olitronik's Pro OUT. Note that all of this is available in black as well, which fits the look.

Lastly, MIDI. Now, this is something the System 700 Block 1 didn't have. However, it DID have the keyboard interface which allowed multiple channels of control for CV/gate to Block 1 and other Blocks. My suggestion would be Befaco's MIDI Thing, which gives you four channels of CV/gate, plus clocking...which might be handy if you try and replicate the sequencer block later on. And the look fits, plus it's a rather simple MIDI to CV, which would fit with the simpler implementation found on Block 1's keyboard interface.

This isn't at all a bad idea, especially since Pharmasonic has replicated the primary modules for the most part. The only stumbling block might be the sequencer, if you opt to continue on and recreate the entire System 700, because that used a weird 12-stage x 3 setup, sort of like a mutated Moog 960 etc. But continuing on while using the Pharmasonics as the basis is also much cheaper than trying to source an original System 700; even with Eurorack being more spendy these days, the resulting build would still come in at a price far less than a used original System 700.

Excellent feedback, thank you! I'm glad you think that this project is not a fool's errand.

I had not considered rack widths beyond 104hp based on typical sizes I was seeing in commercial cases, but I do now see that 126hp is indeed an option for a more authentic 2-row layout. I do plan to build the case myself out of simple box-jointed pine boards or plywood, and already have 3 sets of 84hp rails purchased for the project, but I suppose that I can save those for one of the wing blocks ... you assume correctly that I have considered building those as well if this initial project is a success!

I have not otherwise looked at genuine spring units within the context of Eurorack, but I will do some research on that. Your talk of effects reminds me of my pedal board full of guitar effects (including some nice reverbs). I ought to consider an effects send-return that I could use to patch into that. If anything, that could offload rack space used for effects in favor of what I already have.

I do like the the look of that Olitronic Pro Out, and the 2hp MIDI module is what I currently have on hand, which is the only reason why it's in there. I'll need to do some research to better understand what this unit would and would not allow for compared to other interfaces with more gate/CV outs.

The sequencer solution will probably deviate from the original, in that I don't tend to write waltzes so am not sure how I would approach a 12-step sequencer other than setting it to run 8 steps and ignoring the last 4 steps-- a strange design choice by Roland indeed! I do like the idea of a sequencer "block," but want to focus on getting this first block done before I commit to others. Block 1 is daunting enough, as I'm DIY'ing all the Pharmasonic modules, have fairly limited experience with electronics and soldering, and this is my 1st forray into Eurorack.

Based on your excellent input, I've updated my design:

Pharmasonic SYS-700

I'm hoping to keep the cost for the project to about $1400US for the Pharmasonic modules and case, which is certainly better priced than buying an original System 700!

Based on your